Fuel cells are a device directly converting chemical energy of fuel and air to electricity and heat through an electrochemical reaction. Unlike existing power generating technologies choosing processes of fuel combustion, steam generation, turbine driving and generator driving, fuel cells do not have combustion processes or driving devices, and therefore, is a new power generating technology concept that does not induce environmental problems while providing high efficiency. Such fuel cells are pollution free power generation since air pollution substances such as SOx and NOx are hardly discharged and generation of carbon dioxide is also small as well, and have advantages of low noises and non-vibration.
Fuel cells employ various types such as phosphoric acid fuel cells (PAFC), alkali fuel cells (AFC), polymer electrolyte membrane fuel cells (PEMFC), direct methanol fuel cells (DMFC) and solid oxide fuel cells (SOFC), and among these, solid oxide fuel cells are based on low activated polarization and thereby have low overvoltage, and have small irreversible loss, and accordingly, have high power generation efficiency. In addition, carbon or hydrocarbon-based materials may be used as fuel as well as hydrogen leading to a wide fuel choice, and high-priced precious metals are not required as an electrode catalyst since reaction rates at electrodes are high. Besides, temperatures of heat released incidental to the power generation are very high, which is highly useful. Heat generated in a solid oxide fuel cell may be used not only in fuel reformation, but also as an energy source for industry or cooling in a cogeneration system.
When examining a basic operation principle of a solid oxide fuel cell (SOFC), a solid oxide fuel cell is basically a device generating power through an oxidation reaction of hydrogen, and in an anode that is a fuel electrode, and a cathode that is an air electrode, an electrode reaction as in the following Reaction Formula 1 is progressed.Air electrode: (½)O2+2e−→O2−Fuel electrode: H2+O2−→H2O+2e−Whole Reaction: H2+(½)O2→H2O  [Reaction Formula 1]
In other words, electrons reach an air electrode through an external circuit, and at the same time, oxygen ions generated in the air electrode are transferred to a fuel electrode through an electrolyte, and in the fuel electrode, hydrogen and the oxygen ions bond to produce electrons and water.
A solid oxide fuel cell is formed with dense electrolyte layers, and a porous air electrode layer and a fuel electrode layer as electrodes placed between the electrolyte layers, and an electrode reaction occurs at boundaries of the electrolyte layers and the electrode layers. In order to increase solid oxide fuel cell efficiency, reaction sites at the boundaries need to be increased, and accordingly, increasing an area of a triple phase boundary (TPB) where gas, an electrolyte and an electrode meet has been required, and as one of the efforts to increase such a reaction area, studies on a method for improving cell performance by increasing a surface area of an electrolyte have been discussed.